1. The Field of the Invention
The present invention relates to holography. In particular, the present invention is directed to a method and system for re-writing in a holographic storage medium.
2. Description of the Related Technology
Holographic techniques for storing images are well known. Such techniques are commonly used to store images in a variety of different applications. Holographic memory is a prospective technology for massive data storage, with the unique advantages of high storage density, fast read/write rate, non-volatility, and no moving parts. Ideally, holographic memory technology may be capable of storing hundreds of billions of bytes of data, transferring them at a rate of a billion or more of bits per second and selecting a randomly chosen data element in 100 microseconds or less.
To date, no state-of-the-art electronic memory technology offers all of the advantages that may be obtained with holographic memory. Dynamic Random Access Memory (DRAM) or Static Random Access Memory (SRAM) are both volatile and require constant refreshing. Electrically Erasable Programmable Read Only Memory (EEPROM) is nonvolatile and has read/write functionality, but it has less storage capacity and a very slow rewrite speed. FLASH memory is nonvolatile and has read/write capability but it too has less storage capacity.
Many devices (e.g., compact discs and digital video discs) use light to store and read data. However, prior art optical storage methods have limited transfer rates and capabilities. To overcome the disadvantages of the prior art, holographic memory may be used. Holographic memory stores information beneath the surface of the recording medium and uses the volume of the recording medium for storage. To date, holographic memory systems have been limited with respect to speed due to the need for re-encoding data and/or reading the data from the storage medium.
Holographic data storage is interesting from a business as well as scientific perspective. At least two companies today claim storage media capable of write once, read many (WORM) for storage markets such as video archival and medical applications. One company, Aprilis, Inc. (a division of STX Group), is producing 120 mm discs for which 400 GB storage capacity and 125 MB/s data transfer rate is claimed to be possible when used in a properly designed disc drive system. A second company, In-Phase Technologies (now controlled by Signal Lake), claims 300 GB and 20 MB/s in the near term with the hope to reach terabyte densities in the future.
While these companies are able to produce large capacity storage devices, they are not able to achieve the desired re-writing capabilities.
In order to provide a commercially viable product that uses holographic memory, there is a need in the field to employ improved micro-mirror beam steering devices for angle multiplexing in a holographic storage system.